Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “selective extraction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed2003

Smooth muscle raft-like membranes.

We developed a method for extracting raft-like, liquid-ordered membranes from the particulate fraction prepared from porcine trachealis smooth muscle. This fraction, which contains most of the plasma membrane in this tissue, was homogenized in the presence of cold 0.5% Triton X-100. After centrifugation, membranes containing high contents of sphingomyelin (SM) and cholesterol and low phosphatidylcholine (PC) contents remained in the pellet. Thirty-five millimolar octyl glucoside (OG) extracted 75% of these membranes from the Triton X-100-resistant pellet. These membranes had low buoyant densities and accounted for 28% of the particulate fraction lipid. Their lipid composition, 22% SM, 60% cholesterol, 11% phosphatidylethanolamine, 8% PC, <1% phosphatidylinositol, and coisolation with 5'-nucleotidase and caveolin-1 suggest that they are liquid-ordered membranes. We compared characteristics of OG and Triton X-100 extractions of the particulate fraction. In contrast to Triton X-100 extractions, membranes released from the particulate fraction by OG were mainly collected in low buoyant fractions at densities ranging from 1.05 to 1.11 g/ml and had phospholipid and cholesterol contents consistent with a mixture of liquid-ordered and liquid-disordered membranes. Thus, OG extraction of apparent liquid-ordered membranes from Triton X-100-resistant pellets was not due to selective extraction of these membranes. Low buoyant density appears not to be unique for liquid-ordered membranes.

5'-Nucleotidase↗
PubMed2005

Molecularly imprinted polymers for biomolecular recognition.

Molecular imprinting of polymers is a concept for the synthetic formation of structurally organized materials providing binding sites with molecular selectivity. Compared to biological receptors, these polymeric recognition systems have the advantage of superior chemical and mechanical stability with potential applications in areas such as biomimetic catalysis and engineering, biomedical analysis, sensor technology, or the food industry. In particular, molecularly imprinted polymers (MIPs) providing selectivity for biorelated molecules are gaining substantial importance. In this context, a self-assembly approach for the synthesis of imprinted polymers against the flavonol quercetin is presented, which is exemplary for the biologically relevant group of flavonoid compounds. The creation of synthetic selective recognition sites for this biomolecule is demonstrated by comparing the separation capabilities of imprinted and nonimprinted polymer particles for several structurally related molecules via high-performance liquid chromatography experiments. The developed quercetin-MIP enables selective extraction of quercetin even from complex mixtures, demonstrating the potential for designing biomimetic recognition materials with improved selectivity for biomolecules with tunable functionality at a nanoscale.

Chemistry Techniques, Analytical↗
PubMed2003

Determination of a flame retardant hydrolysis product in human urine by SPE and LC-MS. Comparison of molecularly imprinted solid-phase extraction with a mixed-mode anion exchanger.

Diphenyl phosphate is a hydrolysis product and possible metabolite of the flame retardant and plasticiser additive triphenyl phosphate. A molecularly imprinted polymer solid-phase extraction (MISPE) method for extracting diphenyl phosphate from aqueous solutions has been developed and compared with SPE using a commercially available mixed-mode anion exchanger. The imprinted polymer was prepared using 2-vinylpyridine (2-Vpy) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and a structural analogue of the analyte as the template molecule. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with both aqueous standards and spiked urine samples, by comparing recovery and breakthrough data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from aqueous solutions resulted in more than 80% recovery. Adsorption by the molecularly imprinted polymer (MIP) was non-selective, but selectivity was achieved by selective desorption in the wash steps. Diphenyl phosphate could also be selectively extracted from urine samples, although the urine matrix reduced the capacity of the MISPE cartridges. Recoveries from urine extraction were higher than 70%. It was important to control pH during sample loading. The MISPE method was found to yield a less complex LC-ESI-MS chromatogram of the urine extracts compared with the mixed-mode anion-exchanger method. An LC-ESI-MS method using a Hypercarb LC column with a graphitised carbon stationary phase was also evaluated for organophosphate diesters. LC-ESI-MS using negative-ion detection in selected ion monitoring (SIM) mode was shown to be linear for diphenyl phosphate in the range 0.08-20 ng microL(-1).

Anion Exchange Resins↗
PubMed1995

Determination of intracellular levels of 6-mercaptopurine metabolites in erythrocytes utilizing capillary electrophoresis with laser-induced fluorescence detection.

Capillary electrophoresis proved to be a useful technique for the analysis of intracellular levels of 6-thioguanosine mono-, di-, and triphosphate with analysis times of 20 min. Conditions required for baseline separation of the thioguanine nucleotides consisted of a 25 mM KH2PO4 (pH 8.0) buffer and a separation voltage of +28 kV. Laser-induced fluorescence detection (lambda ex = 325 nm, lambda em = 410 nm) of the thioguanine nucleotide metabolites of 6-mercaptopurine (6-MP) was possible following oxidation of the thiol functionality. Tedious extraction procedures involving mercury cellulose resins or phenyl mercury adduct formation, which had been required previously for the selective extraction of thiopurines from erythrocytes, were unnecessary due to the overall specificity of the approach. However, the inclusion of 50 mM EDTA in the sample preparation was required to inhibit the anabolic/catabolic enzymatic activity, which was responsible for the degradation of the analytes. The method demonstrated linearity from 5 to 1700 pmol/100 microliters red blood cells for the three analytes (RSDs < or = 8%). The feasibility of the method was demonstrated for the quantitation of 6-thioguanine nucleotides in patients receiving either oral or intravenous 6-MP therapy.

Electrophoresis↗
PubMed2002

Determination of pesticide residues in red wines with microporous membrane liquid-liquid extraction and gas chromatography.

A sample pretreatment method based on microporous membrane liquid-liquid extraction (MMLLE) was developed for the subsequent gas chromatographic determination of pesticides in wine. MMLLE provided efficient and selective extraction with enrichment factors in the range 3-13. The gas chromatographic separation was carried out using on-column injection and flame ionization detection. The method was linear, repeatable and sensitive. The limits of quantification were better than 0.006 mg/L for all the analytes except for iprodione (0.37 mg/L). The method was applied to the determination of pesticides in several red wines of different origin.

Chromatography, Gas↗
PubMed2002

Resolution of uncertainty of a four-stage sequential extraction procedure using analysis of variance.

Sequential extraction procedures are mostly applied to soils and sediments. Investigations were made for testing the applicability of a selected extraction scheme on spoil pile material. Therefore, different spoil pile samples from uranium mining were extracted into four steps (exchangeable, reducible, oxidizable, and aqua regia soluble phase) and the contents of the elements Cr, Cu, Fe, K, Ni, and Zn were analyzed. To substitute the sequential extraction by a sequence of single extractions and thus keep uncertainties of extraction on a low level, both procedures were compared regarding conformity of their results. The effects of sample handling as well as those of analysis on the measured metal contents were determined by means of analysis of variance and sources of uncertainties were discussed.

Journal Article↗
PubMed1976

A solvent system for delipidation of plasma or serum without protein precipitation.

A technique has been developed which attains in 30 minutes complete removal of triglyceride, cholesterol, phospholipid, and unesterified fatty acids from plasma without protein denaturation. Plasma is agitated at room temperature with a mixture of butanol and di-isopropyl either in a 40:60 (v/v) ratio. The plasma proteins, including the apolipoproteins, remain in solution in the aqueous phase, while the organic phase contains the dissolved lipids. The phases can easily be separated by low speed centrifugation. Different lipids are simultaneously extracted, but the rate of extraction is most rapid for unesterified fatty acids, followed by triglyceride, cholesterol, and phospholipid at, respectively, decreasing rates. Selective extraction of unesterified fatty acids, triglyceride and total cholesterol can be achieved by di-isopropyl ether alone. Ionic strength and pH are not altered by these procedures.

Autoanalysis↗
PubMed1991

Bioequivalence assessment of diltiazem preparations by means of discriminant analysis of data from solid-phase extraction and liquid chromatography.

A solid-phase extraction technique for sample clean-up coupled with a new LC procedure is reported for the assay of diltiazem in plasma. The use of disposable cartridges provides selective extraction and easy automation. A new LC system based on LiChrospher RP 60 Select B columns is described. For routine analysis, the procedure provides a rapid simultaneous clean-up of several samples prior to chromatography and reproducible recoveries over a concentration range of 10-800 ng. The procedure was used to analyse the plasma samples from a bioequivalence study of three commercial diltiazem preparations. The pharmacokinetic parameters in 12 healthy male volunteers were determined and the assessment of bioequivalence was conducted by discriminant analysis.

Adult↗
PubMed2006

Extraction spectrophotometric determination of aluminum in dialysis concentrates with 3,5-ditertbutylsalicylfluorone and ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate.

The paper describes a highly sensitive and selective extraction spectrophotometric method for determination of aluminum in dialysis concentrates with new reagent 3,5-ditertbutylsalicylfluorone abbreviated as DTBSF, in which the ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C4tmsim][PF6] was used as novel medium for liquid/liquid extraction of aluminum(III). Under optimal condition, DTBSF reacted with aluminum(III) to form a neutral Al-DTBSF complex rapidly, the complex was then extracted into the [C4tmsim][PF6] phase, the absorbance of the complex in ionic liquid at 542 nm was recorded and used to determine aluminum(III). The apparent molar absorptivity of the complex and detection limit were found to be 3.52x10(6) l mol(-1) cm(-1) and 0.06 microg/l, respectively. The absorbance of the complex at 542 nm increases linearly with the concentration of aluminum(III) up to 3 microg of aluminum(III) in 250 ml of aqueous solution. The interference study show the determination of aluminum is free from interferences of almost all positive and negative ions found in dialysis concentrate samples. The determination of aluminum in dialysis concentrates were carried out by the present method and electrothermal atomic absorption spectrometry (GTAAS). The results were satisfactorily comparable so that the applicability of the proposed method with the ionic liquid system was also investigated. Moreover, the synthesis of and conditions for the formation and extraction of Al-DTBSF complex were investigated as well.

Aluminum↗
PubMed1981

Phosphoric acid-its use in the extraction of RNA: staining of DNA in mammalian tissue sections.

This communication presents highly satisfactory methods for the demonstration of DNA in animal materials. The method involves selective extraction of RNA with concentrated, 90% or 75% phosphoric acid of 5 degrees C for 20, 40 and 120 min, respectively, followed by staining with aqueous solutions of basic dyes, such as setoglaucine, setocyanine, pinakryptol green 2) and alcoholic aniline blue without SO2. Perfect blue nuclei were seen when staining was performed with aqueous solutions of setoglaucine and setocyanine at pHs 3.5 and 4.0 to 4.5, respectively. Sections of tissues from which RNA has been extracted and then hydrolysed in 6 N HCl at 28 degrees C for 15 min followed by staining with these dyes also revealed perfect colouration of the nuclei. Acid-hydrolysed sections when stained with alcoholic aniline blue-SW2 prepared with N HCl and sodium thiosulphate revealed nuclei of magenta colour, and sections from whcih RNA has been extracted and then hydrolysed in hydrochloric acid and stained with this dye-reagent revealed nuclei of purplish colour. Sections of tissues fixed in Carnoy, 10% buffered neutral formalin as well as paraformaldehyde were found to be most suitable for staining with these dyes. The in situ absorption spectra of nuclei stained with aqueous solutions of setoglaucine, setocyanine and alcoholic aniline blue without SO2, after extraction of RNA as well as those of nuclei in tissue sections from which RNA has been extracted and then acid-hydrolysed and stained with alcoholic aniline blue-SO2 have been presented. Also presented herein are absorption data of nuclei in tissue sections which wee hydrolysed in hydrochloric acid and then stained with alcoholic aniline blue-SO2. Some implications of these findings have been discussed.

Aniline Compounds↗
PubMed2002

Defining and using microbial spectral databases.

This work shows how fingerprints of mass spectral patterns from microbial isolates are affected by variations in instrumental condition, by sample environment, and by sample handling factors. It describes a novel method by which pattern distortions can be mathematically corrected for variations in factors not amenable to experimental control. One uncontrollable variable is "between-batch" differences in culture media. Another, relevant for determination of noncultured extracts, is differences between the cells' environmental experience (e.g., starved environmental extracts versus cultured standards). The method suggests that, after a single growth cycle on a solid medium (perhaps, a selective one), pyrolysis MS spectra of microbial isolates can be algorithmically compensated and an unknown isolate identified using a spectral database defined by culture on a different (perhaps, nonselective) medium. This reduces identification time to as few as 24 h from sample collection. The concept also proposes a possible way to compensate certain noncultured, nonisolated samples (e.g., cells concentrated from urine or impacted from aerosol or semi-selectively extracted by immunoaffinity methods from heavily contaminated matrices) for identification within half an hour. Using the method, microbial mass spectra from different labs can be assembled into coherent databases similar to those routinely used to identify pure compounds. This type of data treatment is applicable for rapid detection in biowarfare and bioterror events as well as in forensic, research, and clinical laboratory contexts.

Algorithms↗
PubMed2001

[Supercritical fluid extraction of beta-elemene under lower pressure].

A method has been developed for the extraction and analysis of the active component beta-elemene from Rhizoma Atractylodis Macrocephalae by supercritical fluid extraction with CO2 containing ethanol. The article discusses some factors such as pressure, temperature and modifier that affect the selectivity. Class-selective extraction has been performed by varying the pressure. beta-Elemene could almost be extracted completely at lower pressure (12.0 MPa) and its relative amount was raised from 4.8% under higher pressure to 8.0% for lower pressure.

Atractylodes↗
PubMed1976

Partial puridication of a membrane protein from human erythrocytes involved in glucose transport.

In an attempt to determine which membrane proteins are essential to the stereospecific uptake of D-glucose, isolated human erythrocyte membranes were exposed to a variety of reagents capable of selectively extracting various membrane proteins. These reagents included EDTA, lithium 3,5-diiodosalicylate, sodium iodide, and 2,3-dimethylmaleic anhydride. Selective elution of spectrin and Components 2.1, 2.2, 2.3, 4.1, 4.2, 5, and 6 representing 65% of the ghost protein has no effect on the uptake of D-glucose. All of the sugar transport proteins are associated with a membrane residue consisting of the proteins of Bands 3, 4.5, and 7, the periodic acid-Schiff-sensitive glycoproteins, and ghost phospholipids. Specific cross-linking of the proteins of Band 3 of ghosts by the catalyzed oxidation of intrinsic sulfhydryl groups with the o-phenanthroline-cupric ion complex inhibits D-glucose uptake and alters the relative electrophoretic mobility of Band 3 proteins in sodium dodecyl sulfate-polyacrylamide-agarose gels. This uptake activity and the relative mobility of Band 3 proteins are recovered upon reversal of the cross-linking reaction by reduction with 2-mercaptoethanol. These results and other observations indicate that the D-glucose transport protein is an intrinsic component of the hydrophobic structure of the erythrocyte membrane and may be associated with the proteins of Band 3 which are glycoproteins spanning the membrane bilayer. It is proposed that D-glucose transport occurs through a water-filled channel formed by specific subunit aggregates of the transport proteins in the erythrocyte membrane rather than by rotation of the protein within the plane of the membrane.

Biological Transport, Active↗
PubMed2003

Organomercurial removal from vaccine production wastewaters in a supported liquid membrane bioreactor.

Vaccine production effluents are strongly polluted with thiomersal, a highly toxic organomercurial compound, for which there is presently no remediation technology available. This work describes a new remediation process based on the extraction of thiomersal from the wastewater to a biological compartment, where it is degraded by a microbial strain. The selective extraction of thiomersal is achieved by using an ionic liquid immobilized in a porous membrane. In the biological compartment, thiomersal is degraded to metallic mercury, under aerobic conditions, by a Pseudomonas putida strain. The utilization of ionic liquids in supported liquid membranes for thiomersal transport, and the kinetics of thiomersal biodegradation by a Pseudomonas putida strain are presented and discussed.

Biodegradation, Environmental↗
PubMed2002

Screening for postmenopausal osteoporosis: a review of the evidence for the U.S. Preventive Services Task Force.

BACKGROUND: Although osteoporotic fractures present an enormous health burden, it is not clear whether screening to identify high-risk persons is appropriate. PURPOSE: To examine evidence on the benefits and harms of screening postmenopausal women for osteoporosis. DATA SOURCES: MEDLINE (1966 to May 2001), HealthSTAR (1975 to May 2001), and Cochrane databases; reference lists; and experts. STUDY SELECTION: English-language abstracts that included original data about postmenopausal women and osteoporosis and addressed the effectiveness of risk factor assessment, bone density tests, or treatment were included. DATA EXTRACTION: Selected information about patient population, interventions, clinical end points, and study design were extracted, and a set of criteria was applied to evaluate study quality. DATA SYNTHESIS: No trials of the effectiveness of screening have been published. Instruments developed to assess clinical risk factors for low bone density or fractures have moderate to high sensitivity and low specificity. Among different bone density tests measured at various sites, bone density measured at the femoral neck by dual-energy x-ray absorptiometry is the best predictor of hip fracture. Women with low bone density have approximately a 40% to 50% reduction in fracture risk when treated with bisphosphonates. CONCLUSIONS: Population screening would be based on evidence that the risk for osteoporosis and fractures increases with age, that the short-term risk for fracture can be estimated by bone density tests and risk factors, and that fracture risk can be reduced with treatment. The role of risk factor assessment and different bone density techniques, frequency of screening, and identification of subgroups for which screening is most effective remain unclear.

Aged↗
PubMed1985

Measurement of propericiazine in plasma by capillary gas chromatography and selected ion monitoring detection.

A new method, based upon a selective extraction and gas chromatographic/mass spectrometric analysis, was developed to monitor the effect of combined haemoperfusion-haemodialysis treatment in a case of propericiazine poisoning. The method relies on the selected ion monitoring of the acetate derivatives of propericiazine and its internal standard fluphenazine, after their extraction from 1 ml of alkalinized plasma with n-hexane:isopropanol (8:2, v/v), back-extraction into an acidified water phase, realkalinization and extraction with n-hexane: isopropanol, derivatization with acetic anhydride and gas chromatography on a short (12 m) OV-101 fused silica capillary column. The described procedure is specific and provides between-assay variability of 4.8% CV at 5 micrograms 1(-1) plasma concentration. The method enables quantification down to 1 microgram 1(-1) and hence demonstrates sufficient sensitivity to permit pharmacokinetic or drug monitoring studies.

Female↗
PubMed1979

An improved extraction method for plasma steroid hormones.

An easy and rapid column chromatographic method for the extraction of steroid hormones from plasma is presented. It permits the nearly quantitative separation of the steroids in a single step with smaller expenditure of time and work as compared to the usual liquid-liquid extraction. Problems of emulsions are eliminated. Furthermore, fractionated separation of hormones from plasma is possible. A simple procedure for the selective extraction of estriol (isolated from estrone and estradiol) is described.

Chromatography↗
PubMed2005

Disposable ionic liquid coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in paints followed by gas chromatography-flame ionization detection.

Solid-phase microextraction (SPME) with a disposable ionic liquid (IL) coating was developed for headspace extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) in paints. The SPME fiber was coated with IL prior to every extraction, then the analytes were extracted and desorbed on the injection port of gas chromatography, and finally the IL coating on the fiber was washed out with solvents. The coating and washing out of IL from the fiber can be finished in a few minutes. This disposable IL-coated fiber was applied to determine BTEX in water-soluble paints with results in good agreement with that obtained by using commercially available SPME fibers. For all the four studied paints samples, the benzene contents were under the detection limits, but relatively high contents of toluene, ethylbenzene and xylenes (56-271 microg g(-1)) were detected with spiked recoveries in the range of 70-114%. Compared to the widely used commercially available SPME fibers, this proposed disposable IL-coated fiber has much lower cost per determination, comparable reproducibility (RSD < 11%), and no carryover between each determination. Considering that IL possess good extractability for various organic compounds and metals ions, and that task-specific IL can be designed and synthesized for selective extraction of target analytes, this disposable IL coating SPME might has great potential in sample preparation.

Benzene↗